2007 Chrysler Aspen 5.7 Hemi.. replaced thermostat, purged to the best of my knowledge... now when it's cold I can let it run for an hour and the temp guage stays 2 notches below half way mark, very little heat... rev it up a bit to get everything circulating and then vents turn ice cold,gauge starts to climb, check under hood and upper radiator hose is collapsed, loosen the cap and it pops out and I get heat galore and can drive all day no issues..... let it cool down for a few hours, start it up and same thing... was told radiator cap so bought a new one... no diference... only happens when it is cold.... today i let it run for 45 minutes... top radiator hose was warm by the thermostat but cold by the radiator, hose again sucked in... this time when I went to loosen the radiator cap it was like stuck on, I pried it up and heard a big whoosh and the hose once again went back to normal so I got brave and took it on a 77 mile trip.... interstate and small towns... the gauge never went above the half way mark... so it's been sitting 3 hours again, just went out to try it again and same thing.... barely warm gauge is at half way mark, rev it up, gauge goes up, look under hood, radiator hose collapse, loosen cap, hose goes back to normal and I have heat... oh and the hose is new too.... any suggestions?? someone suggested head gasket was out and if thats the case, good by Aspen.

 

also should note that this only happens when it is cold outside... 3 below right now.... couple days ago it was in the 40's and had no issues with the hose, overheating, or hot air out of vents

 

Sounds to me like you have an air pocket somewhere in the system. Getting all the air out can be difficult at times. What I usually do is run the engine with the radiator cap off. Fill the radiator to the top. Tap and squeeze the upper hose while watching the level in the radiator. Then get someone to raise the RPM's up a little to get the water flowing through the system. Again, tapping and squeezing the upper hose while RPM's are up and keeping level full in radiator. You may find at one point a large drop in coolant all of a sudden. This means you have "burped" the air bubble out. Top it off again and continue until level remains full with RPM's up. Then cap it while RPM's are up. If you drop RPM's before capping, it will overflow back out of radiator, so be sure to cap before that happens.

 

Sounds like a radiator now allowing coolant to pass through. IS the lower hose hot and the upper cold?

 

they mentioned about another auxilary waterpump to circulate

 

there is only one water pump in this setup